Recreational and other vehicles are sometimes outfitted with irregular shaped windows, for example trapezoidal windows. Existing roller shades for trapezoidal windows are designed to enable the roller tube on which the shade is wound to move laterally over a support tube so that the shade can move laterally with the roller tube to fully cover the bottom of the window. For example, lateral movement of the roller tube may be particularly important when the shade is designed to occupy a confined space such as when the trapezoidal window is at the front of a vehicle, where it may be adjacent and orthogonal to an angled windshield. The shade may be shaped to be closely fitted to the window, for example in the case of a trapezoidal window, using a shade cut in a matching trapezoidal shape. However, even with a shade of matching shape, without being able to move laterally, the shade would not fully cover the window at various heights over the range of vertical movement of the shade. For example, if the roller tube did not move laterally there would either be a gap in coverage near at the corner of the window immediately adjacent the windshield or the shade could not be lifted fully without running up against the windshield.
To avoid gaps in coverage using a laterally moving shade, the lateral starting position of the shade may need to be adjusted on-site.
Furthermore, depending on the interior design of the vehicle cabin, the mounting bracket might be organized to fit behind a valence. To make the bottom of the shade accessible from beneath the valence, particularly in the case of manually operable shade, it is desirable to be able to set an upper limit of movement for the bottom end of the shade, when the shade is installed, for example, so that the bottom end of shade does not disappear behind the valence, when fully retracted.
Existing trapezoidal roller shade designs are not well-suited for such upper limit or lateral position adjustments. Since the shade is designed to move laterally when descending, lateral movement of the roller tube is preferably designed to be linked to its rotation about the axis of the roller tube. In existing designs, a spindle having a helical exterior groove is used to convert the rolling motion about the axis of the roller tube into lateral movement. This is accomplished by using an internally threaded spindle nut which travels axially (along the axis) with respect to the external thread of the spindle. Rotation of the spindle nut about the axis of the spindle is rotationally linked to the roller tube so that the two co-rotate. Since the spindle nut rotates together with the roller tube, the spindle nut travels axially over the spindle to convert the rotation of the roller tube into axial movement of roller tube over a support tube.
In the afore-described prior art design, the spindle and spindle nut are housed within a hollow axial bore in the support tube which is visible via a long narrow aperture or slot in the wall of the support tube. The roller tube is secured to the spindle nut with a set screw receivable in an exterior aperture in the roller tube and a corresponding exterior threaded aperture in the spindle nut. This threaded aperture in the spindle nut (there may be more than one such aperture) is visible through this slot in the support tube however since the most of the length of the support tube is located in the cylindrical hollow of the roller tube, except the threaded aperture, the slot and the spindle nut are normally concealed by the roller tube. This makes it difficult to adjust upper limit of movement of the bottom end of the shade without disassembling the roller shade assembly.
Lateral adjustment of the starting position of the roller tube on the support tube necessitates removal of the set screw to adjust the axial position of the spindle nut in relation to the support tube in a manner that axially re-aligns the apertures in the roller tube and spindle nut. However, this adjustment concomitantly adjusts the upper limit of movement of the bottom end of the shade, as explained hereafter, which either causes the bottom end of the shade to disappear behind the valence or ends the course of its upward travel prematurely.
Adjustment of the position of the roller tube relative to the support tube, on site, is accomplished by rotating a wheel located at one end of the roller shade assembly near the mounting bracket. The wheel rotates co-axially with the spindle and is rotationally linked to the spindle to co-rotate therewith and rotate of the spindle about its own axis. Rotation of this adjustment wheel also co-rotates a threaded shaft which is linked to the spindle. Co-rotation of the threaded shaft concomitantly adjusts the upper limit of the bottom end of the shade by causing axial movement of an internally threaded axially driven element configured to rotate on the threaded shaft in the manner of a nut. This alters the distance of the axially driven element from the position of a stop element against which the axially driven element abuts at the end of its course of travel over the threaded shaft, this distance in turn defining the maximum number of revolutions of the roller tube.
Accordingly, in prior art designs, adjustment of the axial position of the spindle nut using an adjustment wheel undesirably adjusts the upper limit of movement of the bottom end of the shade. This is a cumbersome and ineffective solution for adjusting the starting axial position of the roller tube on the support tube and the maximum distance of upward travel of the bottom end of the shade, when the shade is being installed.
Accordingly, there is a need for a less cumbersome and more effective manner of making such adjustments in laterally moving shades.